Leafcutting and Diet Selection: Relative Influence of Leaf Chemistry and Physical Features

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The effects of leaf toughness, trichome characteristics, nutrient and water availability, and secondary chemistry on diet selection by the leafcutting ant Atta cephalotes were determined using individuals of 49 woody plant species from a tropical deciduous forest in Costa Rica. The palatability of plants was measured by presenting whole leaves to leafcutting ant foragers on trails and counting the number of pieces cut from leaves. The effectiveness of physical barriers to leaf cutting was evaluated by measuring the speed with which ants were able to cut leaves of varying toughness, trichome densities, and trichome lengths. Ecological Society of AmericaPlant secondary chemistry was highly correlated with the relative palatability of leaves, while palatability was only marginally correlated with trichome characteristics and plant nutritional quality and was uncorrelated with leaf toughness and water content. Highly palatable leaves generally contained hydrolyzable tannins, while most unpalatable leaves possessed nonpolar extracts found to deter leaf cutting in laboratory bioassays. Within the subset of highly palatable plants, leaf protein content was positively correlated with the number of pieces cut, indicating that secondary chemistry and nutrient availability interact to determine palatability. Decreases in plant palatability over time paralleled decreases in protein content. Ant size was the most important variable determining the rate at which ants cut leaves. Trichome characteristics were uncorrelated with the rate at which leaves were cut, while leaf toughness explained a small amount of the variance in cutting rate.The results suggest that leaf toughness and trichome characteristics within the ranges encountered by leafcutting ants in this tropical deciduous forest do not generally deter attack by ants. Instead, the results are consistent with the idea that leafcutting ants use a combination of plant secondary chemistry and nutrient availability to evaluate the quality of leaves.

Two fungal symbioses collide: endophytic fungi are not welcome in leaf-cutting ant gardens

“…The ants defoliate a wide diversity of plants in neotropical forests and often have an enormous effect on local flora and distribution of nutrients (Howard 1988;Farji-Brener & Silva 1996;Wirth et al 2003;Sternberg et al 2007). The worker ants cut leaves, carry them to the nest, clean them and use them to provision their fungal cultivar.…”

Leaf fracture toughness and sclerophylly: their correlations and ecological implications

“…Penetrometers have been frequently employed for measuring leaf toughness, particularly in investigations of herbivory (Feeny, 1970;Cherrett, 1972;Schultz, Nothnagle & Baldwin, 1982;Waller, 1982;Coley, 1983;Lowman & Box, 1983;Raupp, 1985;Ayres & MacLean, 1987;Howard, 1988;Larsson & Ohmart, 1988;Cavalier & Goldstein, 1989;Ernst, 1989;Tuomi et al, 1989;Aide & Zimmerman, 1990;Bjorkman & Anderson, 1990;Jing & Coley, 1990;Medina, Garcia & Cuevas, 1990;Nichols-Orians & Schultz, 1990;Reich et al, 1991).…”

Field colonies of leaf‐cutting ants select plant materials containing low abundances of endophytic fungi

“…Leaf-cutting ant foraging is complex and a variety of factors other than endophyte content have also been found to influence the foraging preferences of leaf-cutting ants including: leaf toughness (Nichols-Orians and Schultz 1989), secondary compounds (Hubbell et al 1983, Howard 1988, nutrient content (Berish 1986, Howard 1988, Farji-Brener 2001, and epiphylls (Mueller and Wolf-Mueller 1991). To further complicate the matter, many of these variables in leaf tissue are covariates.…”